551 



But, even if it were so, it may be questioned whether the ozone 

 would not be at once destroyed when in contact with the carbon- 

 compounds present. It is more probable, however, that the ozone 

 said to be observed in the vicinity of vegetation, is due to the action 

 of the oxygen of the air upon minute quantities of volatile carbo- 

 hydrogens emitted by plants. 



Supposing ozone to be present, it might, however, be supposed to 

 act in a more indirect mariner as a source of combined and assimilable 

 nitrogen in the Authors' experiments, namely, by oxidating the 

 nitrogen dissolved in the condensed water of the apparatus by 

 forming nitrates in contact with the moist, porous, and alkaline 

 soil or by oxidating the free nitrogen in the cells of the older 

 roots, or that evolved in their decomposition. 



Experiments were accordingly made to ascertain the influence of 

 ozone upon organic matter, and on certain porous and alkaline 

 bodies, under various circumstances. A current of ozonous air was 

 passed over the substances for some time daily, for several months, 

 including the whole of the warm weather of the summer ; but in 

 only one case out of eleven was any trace of nitric acid detected, 

 namely, that of garden soil ; and this was proved to contain nitrates 

 before being submitted to the action of ozone. 



It is not, indeed, hence inferred that nitric acid could under no 

 circumstances be formed through the influence of ozone on certain 

 nitrogenous compounds, on nascent nitrogen, on gaseous nitrogen in 

 contact with porous and alkaline substances, or even in the atmosphere. 

 But, considering the negative result with large quantities of ozonous 

 air, acting upon organic matter, soil, &c., in a wide range of circum- 

 stances and for so long a period, it is believed that no error will be 

 introduced into the main investigation by the cause referred to. 



Numerous experiments were made to determine whether free ni- 

 trogen was evolved during the decomposition of nitrogenous organic 

 compounds. 



In the first series of 6 experiments, wheat, barley, and bean-meal 

 were respectively mixed with ignited pumice and ignited soil, and 

 submitted for some months to decomposition in a current of air, 

 in such manner that any ammonia evolved could be collected and 

 estimated. The result was, that, in 5 out of the 6 cases, there was 

 a greater or less evolution of free nitrogen amounting, in two of the 



